According to the related art, since a bandwidth of a frequency domain used in the vehicle radar system is not so broad, a component of a switching frequency generated in a power supply module does not cause a problem.
However, in recent years, as a usable bandwidth is gradually increased, the switching frequency is included in a frequency domain used in a frequency modulated continuous wave (FMCW) radar, which may cause a problem.
In order to solve the above-mentioned problem, U.S. Pat. No. 7,079,073 discloses a method which shifts a switching frequency component of a power supply device of an FMCW radar into an assignable band to move the switching frequency component to the outside of a frequency domain where data exists, thereby avoiding a noise.
However, the above method has the following problems:
First, in order to change a switching frequency, a switching signal output module which includes a clock generator and a frequency setter as hardware is required. Since a mixer and a local oscillator (LO) which outputs various frequencies are further required, adverse influences such as an increased size of the hardware, an increased material cost, and increased complexity are generated.
Second, when a maximum value of a Nyquist frequency and a maximum value of a beat frequency are equal to each other, the switching frequency is unconditionally shifted only to fN. However, in this case, only a part of a function of the switching signal output module is used, so that the other part may be wasted. In an actual system, the maximum value of the Nyquist frequency and the maximum value of the beat frequency are equal to each other in many cases and a width of allocation bands is narrow.
Third, the method used an aliasing bands may vulnerable to Electro Magnetic Compatibility (EMC) than the method used the lowest specific band.